Pretty good book actually ^_^
Only downside is that most of the organizations presented are only god up to CR 12-14, but.. granted, you can mix and match groups together.
I have all the stat-block books of the RPG line, except from Bestiary 6. They are a must to me, as I don't want to expend my time creating foes again and again. Villain Codex is all about foes.
- While NPC Codex arranges the many characters in the book by class, this one arranges them by "Organization".
- The characters are all built to suit a sort of villainous theme, from evil cultists to secret society members to vile arcane scholars to evil druids. There are even pirates.
- Villain codex has new gears, new spells, and some other options that the NPC Codex doesn't. These options to customize the villainous NPCs are also arranged by "Organization".
- You can easily rearrange the members of the many Organizations to make new organizations, and the book gives some guidance on how to do this.
- There are lots of NPCs, with different classes (from hybrid classes to occult classes, or just the classic ones as well).
- You can use it to insert many different foes in your campaigns "on the fly" (they are all ready-to-go NPCs, just like the NPC codex). Its ease to change their race, some class options, and the flavor, so you can adapt them to any setting or adventure.
Concluding:
The main point of the Villain Codex is, as with any "stat-block" book (Bestiary, NPC Codex, Monster Codex), to provide GMs with characters that are already done, ready to be used on the table. There are plenty of options that can be used by players as well. You can somehow look at the characters in it to see how you would build your own Villainous NPCs, or maybe player can look at them and see how they would develop their characters class build...
Anyway, I don't think this book is nearly as useful as a NPC Codex 2 would be (focusing on the base - like the alchemist and the cavalier - and the hybrid classes - like the bloodrager and the hunter), or even as a codex for the many races (NPCs from the races presented in the ARG), but it's still a pretty useful book.
I have it, and I use it all the time.
It's great for dropping whole groups into your campaign. Town watch. Crazy circus. Secret cult. Just flip to the appropriate chapter and you have everything you need to flesh out an environment or encounter.